Vehicle wheel alignment is known to be checked by operators through the use of special brackets that are designed to be movably attached to each wheel and have a central mount, typically a cantilever hub on one face facing the exterior of the vehicle when mounted to the wheel, for known measurement and control instruments to fit thereupon.
These brackets consist of a central body, typically a metal flange, having three arms which radially extend therefrom at 120° from each other and are equipped at their distal ends with grip members facing the tire of a wheel over the tread, to grip upon the grooves of the latter.
The position of the arms, namely their radial position relative to the center of the flange, can be adjusted as needed to move them toward or away from each other, to thereby adapt the brackets to the variety of diameters of commercial wheels.
For this purpose, the distal ends of the arms are bent into an L shape to partially encircle the wheel, in operation, and the grip members consist, for each arm, of clamping jaws with projecting teeth adapted for engagement with the grooves of the tire tread, as mentioned above.
In order to move the arms simultaneously toward and away from the center of the flange, that must coincide with the axis of rotation of the wheel, mutually articulated lever systems are provided, which are controlled by appropriate knobs.
By rotating the knobs in either direction, a movement is simultaneously imparted to all the levers which transfer such movement to the arms, thereby causing them to axially slide in radial directions, guided by guide members provided for this purpose between the arms and the central body.
Accuracy in controls and adjustments for wheel alignment correction requires the bracket apparatus to be mounted in a perfectly centered position relative to the axes of rotation of the wheels.
Therefore, proper positioning of such bracket apparatus is strictly required to provide exact measurements and is typically a matter of skill of the operators, who also have to carry out mounting, removing and measurement operations while ensuring that the wheel rims are not inadvertently damaged.
To obviate this problem, elastic/rubbery pads are placed on the arm shafts, acting as spacers, and designed to abut the side of a wheel tire or rim during mounting and operation of the brackets.
Also in this case, the position of the pads along the shafts should be adjustable to fit the variety of diameters of vehicle wheels.
In prior art brackets, the pads are directly attached to the arms in fixed positions, to be at preset distances from the center of the central body and the centripetal or centrifugal movement of the arms will automatically move the pads toward or away from each other according to the diameters of the wheels.
In other words, a fixed radial distance exists between each jaw and its pad.
This prior art has certain problems.
The first problem is that some bracket types must be manually positioned on the wheels, and this positioning operation only relies on the expertise and accuracy of operators.
Therefore, under certain conditions these bracket types might provide wrong indications, reflecting in wrong data detection and often in inaccurate corrections.
A further problem is that these brackets are not easily handled during a working day because they have a considerable weight and the repeated succession of wheel mounting and removing operations will be harder and harder as time progresses.
In brackets with simultaneous movement of the arms and the pads abutting the sides of the rims or the tires, it may happen that, in spite of an optimal grip position of the jaws on the tire treads, due to the bead height, which may change according to various tire types, the position of the pads, which is fixed relative to the jaws, will become inaccurate relative to the tire bead and hence the position of the pads will not coincide with the tire beads, whereby the abutment and positioning of the bracket on the wheel will become inaccurate, instable or even dangerous for the integrity of the rims.
One object of the invention is to improve the state of the art.
Another object of the invention is to provide a bracket for vehicle wheel alignment control instruments allowing substantially perfect positioning of the instruments relative to the centers of the wheels to obtain accurate measurements, and allow the operators to perform adequate, error-free adjustments.
A further object of the invention is to provide a bracket for vehicle wheel alignment control instruments that is simply positioned, relatively cost effective and easy to use.
In one aspect the invention relates to a bracket for vehicle wheel alignment control instruments as defined in the features of claim 1.
Further features are as set out in the dependent claims.
Therefore, the bracket for vehicle wheel alignment control instruments affords:
perfectly centered positioning of the instruments on the wheels, with respect to the axes of rotation thereof, and inaccuracy-free measurements and adjustments;
wheel rim protection when mounting, operating and removing the brackets, irrespective of the types of tires that have been mounted; and
considerably reduced effort for the operators.